In automobile transmissions, automobile transmission oil seals are used to prevent leakage of fluids such as oil to the outside from edge portions of power shafts and output shafts which protrude from housings of the transmissions.
Various transmission oil seals have been proposed and examples thereof include a sealing member disclosed as an oil seal to be used in a transmission in Patent Document 1. The sealing member is formed of an elastomer such as nitrile rubber, acrylic rubber, silicone rubber, and fluororubber, and provided with a sealing lip.
Moreover, Patent Document 2 discloses a method for forming a fluororesin coating on the rubber surface with an aim of decreasing the sliding resistance of a seal lip portion in an oil seal.
In recent years, improvement in sliding properties of vehicle transmission oil seals is desired along with the demand for higher performance and better fuel economy of engines. For sure, a vehicle transmission oil seal formed of fluororubber or silicone rubber is likely to have better sliding properties compared to a vehicle transmission oil seal formed of acrylic rubber or nitrile rubber. The above-mentioned demand requires further improvement in sliding properties, especially, improvement in sliding properties over the entire speed running range from a low speed running range to a high speed running range.
Patent Document 1: JP 2005-61454 A
Patent Document 2: JP 2006-292160 A